The shaken Boston region was frozen in place Friday morning as authorities combed the region for Boston Marathon bombing suspect Dzhokhar Tsarnaev after his brother, Tamerlan, was killed in a fiery pre-dawn shootout in Watertown, Mass.

The transit system was shut down. No schools opened. Businesses remained closed. The airspace over the city became a no-fly zone. Logan International remained open, but few could reach it. The sports-loving city's Red Sox postponed their evening game at iconic Fenway Park.

The streets of the nation's 10th-largest urban region were empty as most of the 4.5 million residents of the city and surrounding towns were ordered by Massachusetts Gov. Deval Patrick to shelter in place and area hotels found their rooms filled with stranded spring-time tourists.

Across Boston, the anxiety and trauma of the past week could be seen in the pre-dawn hours on worried faces, shaking bodies and silent moments of sobbing.

In parts of Watertown, people sat on corners after being evacuated from their homes and recounted sounds of gun shots and explosions. Sirens and police lights filled streets, stopping traffic continuously. In other areas, closed-off roads and yellow police tape cropped up on new corners hourly.

Families, in pajamas and carrying young children, evacuated on streets, rushing past flags at half-staff. Some, exhausted by a sleepless night, walked slowly and squinted through heavy eyelids.

In one neighborhood, groups of people gathered on roofs straining and leaning to see into streets. The tension was palpable and the sleep deprivation visible on the faces of pacing police officers and reporters moving slowly.

Yet, despite the overwhelming tragedy, signs of support came in signs for free hugs and strangers who offered to take in displaced residents.

Jennifer Kupiec, 38, and her husband, Nadav Kupiec, 41, were evacuated from their condo around 8 a.m. They woke to text messages and phone calls asking whether they were OK.

Standing on a corner in the brisk air, they tried to take in the improbability of such an event touching their lives.

"It's just disturbing that they could be this close," Nadav, an illustrator, said. "It's just sad."

Jennifer said while she knows fellow Bostonians are shocked by the events, she also senses shared resilience.

"We're tough," she said. "I don't sense any hysteria."

Even so, the tension wears at people.

"It makes me feel very unsafe. I don't feel safe going into any public gatherings," said Tufts University senior Nicole Becker of Brookline, Mass., after a sleepless night marred by the booming sound of police and the suspects who allegedly hurled explosives at the officers.

Becker, whose boyfriend attends nearby Harvard, said that stress levels have surged since Monday's bombings and that hearing those booms from her bedroom window didn't ease her fears.

Scott Tingley, 23, said he heard the last of those booms echo through Tufts University's Medford/Somerville campus, about 6 miles northeast of Watertown, within the past few hours. Tingely, a graduate student who photographed the Tufts Marathon Team Monday, said, "To know that there's going to be some closure on the events of Monday is a sign of relief."

Tufts University called and e-mailed its community twice this morning about the MIT and Watertown violence, and school closure on the Medford/Somerville and Boston campuses.

Accepted high school seniors are also on campus for "Jumbo Days," pre-freshman orientation for those interested in attending Tufts. These events will continue with modified scheduling, according to associate director of admissions Daniel Grayson's Twitter account

Boston is one of the most popular "college towns" in the nation with hundreds of thousands of students, many far from the reassurance of their home and parents. But universities such as Harvard and MIT have bombarded them with text alerts updating them on canceled classes and heightened campus security on the locked-down campuses.

Stephanie Chen, a sophomore at MIT, said, "We learned about the shooting at approximately 10 or 11 p.m. last night. At the time, my friends and I were working in one of the public areas in our dorm floor. ... Then we suddenly heard that someone had been shot on MIT's campus. At that point, everyone dropped what they were doing and started listening to the Cambridge police broadcast and started scanning the news to learn what was going on," Chen said.

Since then, Chen said, MIT students have received at least 20 texts from the campus emergency alert system in addition to phone calls detailing more confirmed information.

Locked in her dorm room and reading e-mails from friends, Chen said, "I could tell that a lot of people were genuinely frightened. A lot of people ended up pulling all-nighters just because they couldn't sleep."

But April is also a time when many high school seniors are visiting universities trying to make their final decision on where to attend in the fall. This weekend, the Harvard College Admissions Office had scheduled the events for Visitas, the annual visiting weekend for admitted prospective students that is scheduled for April 20-22.

On Friday, registration for the event was closed and e-mails were sent to all admitted students, nearly 1,000 people, advising them that events may be affected and prospective students who are already on campus and current students who are scheduled to assist with events should stay indoors.

Molly Dillaway, a sophomore at Harvard and Co-Coordinator of Visitas, posted in the Harvard University Class of 2015 Facebook page early this morning, "Visitas is pretty much on hold since the entire campus is shut down."

All the texting, all the police, even the company of college friends were not enough to ease the mind of Hannah Yeung, 20, from Hong Kong, a junior at Boston University.

"What happened to a city I thought was safe and secure? It's hard for future international students to want to come here," said Yeung. "(My parents) are scared, too. They can't do anything but tell me to stay inside. We're not in the same time zone either, so they're staying up, upset that they can't physically be here with me."

MIT freshman Yi Zhong said she and her friends were mourning the murdered police man and expressed their gratefulness for the sacrifice he made that could have saved many lives on campus.

Still, being MIT, problem sets, projects and exams are still on people's minds, although everything that has happened in the past 12 hours has made it difficult for people to focus.

Sophomore Siva Nagarajan, said, "I have a lot of assignments due next week, so I should try to get started. But when I actually do, I don't know whether I'll be able to focus on it or not. I wasn't last night, for sure."

The impact of locking down Boston radiated far from the city.

Massachusetts Port Authority spokesman Matthew Brelis told Today in the Sky that Logan International Aiport was "operating under heightened security" and advised customers to check with their airlines for the status of their flights today before coming to the airport.

If they could get there - or get home after arrival - Brelis noted that taxis are still coming to and from the airport, though he acknowledged that they were "in short supply as of 10 a.m. ET."

JetBlue, the busiest carrier at Boston Logan, notes that the airport is open but Boston customers ticketed to fly through the airport today can change their itineraries without penalty. Rebooked travel must occur by April 22. And United, the nation's biggest carrier, has announced a similar policy.

On Friday morning, Fritz Kuhnlenz, 28, of Brighton, was sitting on a US Airways flight from Washington to Boston, making arrangements to get home from Logan Airport when not even the taxis are allowed on the streets.

His boss at Boston University already told him "to stay home until further notice," but he wanted to reach his home a mile from Watertown, where he lives with his girlfriend.

But, he said, "My girlfriend said the mayor came on TV and said don't go out on the streets, stay in your home. She used the word lockdown. She's worried. She's been a wreck all week."

Even if he can find a ride home," Kuhnlenz said, he's coming back to a changed city, a place where "you always have to watch your back."